1. Field of the Invention
In certain embodiments, the present invention relates to a heat exhaust pipeline and a related heating apparatus adapted for use in semiconductor manufacturing equipment. Embodiments of the invention also relate to a method of controlling the related heating apparatus. More particularly, the invention relates in certain embodiments to a method of controlling a heating apparatus that is capable of heating a residual gas exhausted from a semiconductor manufacturing process to a predetermined temperature.
This application claims the benefit of Korean Patent Application No. 2004-72345, filed Oct. 9, 2004, the contents of which are hereby incorporated by reference in their entirety.
2. Description of Related Art
The complicated sequence of processes used to manufacture semiconductor devices typically includes multiple processes characterized by the use of various gases. During and following the completion of these gas-involved processes, one or more “residual gases” will be generated. In a great majority of cases, these residual gases must be exhausted from the processing environment (e.g., from a process chamber). The process of exhausting residual gases may, however, become greatly complicated by the nature of the residual gases. For example, some residual gases, if allowed to cool below a critical temperature, will solidify into a powder form. This powdered residue can make a genuine mess of the exhaust system.
Consider, for example, the case of ammonia chloride (NH4Cl), which may be generated as a residual gas during commonly used low-pressure chemical vapor deposition (LPCVD) processes. Ammonia chloride begins to convert to a solid crystalline state at temperatures around 80° C., and maintains a gaseous state at temperatures above 150° C.
Aluminum chloride (AlCl3), which may be generated as a residual gas during a plasma etching process, such as those commonly used to etch aluminum, is another ready example of a gas which solidifies at temperatures below a critical temperature, and requires some minimum temperature to maintain itself in a gaseous state.
In order to prevent such residual gases from solidifying and thus accumulating as a contaminate in an exhaust pipeline, a separate heating apparatus is typically installed in the exhaust pipeline. One example of an exhaust pipeline provided with a heating apparatus is disclosed in Japanese Laid-open Publication No. 1996-124866. In this document, a plurality of heating elements are installed in an exhaust pipeline. Each one of the heating elements has a separate sensor, and each of the heating elements and its associated sensor are connected to an automated controller. Through operation of the controller, an integrated control state is displayed on an associated display.
Unfortunately, this approach is not without its flaws. For example, this integrated control approach breaks down if just one of the individual sensors fails. A failed sensor may result in a sectional misdetection of the actual temperature of the heated exhaust pipeline. Such misdetection arises because the single display indicator can not indicate undesired temperature variation in a particular section of the heated exhaust pipeline. In fact, some sections of the heated exhaust pipeline may become greatly overheated—potentially leading to equipment damage.